The railroad industry employs a large variety of different freight railroad cars for transporting various products. Freight railroad cars travel along railroad tracks on front and rear railway car trucks. Each railway car truck typically includes a pair of side frames that extend parallel to each other and that are connected by a bolster. The side frames are supported by front and rear wheel sets. The bolster is typically connected to the side frames via spring assemblies respectively mounted on the side frames. The bolster includes a centrally positioned bolster bowl configured to receive a center plate of a railroad car body.
The typical bolster bowl is circular and includes a depressed middle portion configured to receive a correspondingly shaped circular center plate attached to the bottom of the railroad car body. The circular shape of the bolster bowl and the center plate of the car body enable the railway car truck to pivot laterally (e.g., yaw) while maintaining relative stability of the car body. For example, the bolster bowl enables a railway car truck to pivot based on a curvature of the tracks without substantially affecting the stability of the car body.
Side bearings, and particularly constant contact side bearings, are typically connected to the bolster of each truck of a freight railroad car to provide additional stability for the car body during travel. Two side bearings are typically respectively located on bearing pads on the bolster between the bolster bowl and the side frames (i.e., on opposite sides of the bolster bowl). To provide additional stability for the car body and trucks, the side bearings are configured to continuously maintain contact with the underside of the car body when the freight railroad car is full, and more importantly when the freight railroad car is empty. In this manner, the side bearings provide additional points of contact between the car body and the bolster to provide desired control of the car body and to prevent car body dynamic instances. Each such side bearing typically includes a spring and/or elastomer element configured to apply pressure or forces between the car body and the bolster to prevent or limit such undesired movement of the car body relative to the bolster and side frames. In other words, constant contact side bearings tend to provide a higher level of functionality when a freight railroad car is empty then when it is filled.
FIGS. 1, 2, 3, 4A, 4B, 4C, and 4D generally illustrate sets of commercially available constant contact side bearing assemblies. Each different side bearing assembly shown in FIGS. 4A, 4B, 4C, and 4D is configured to provide a different amount of pre-load. Each different side bearing assembly generally includes a different cage (i.e., one of the cages 116A, 116B, 116C, and 116D respectively shown in FIGS. 4A, 4B, 4C, and 4D), a different elastomer element (i.e., one of the elastomer elements 114A, 114B, 114C, and 114D respectively shown in FIGS. 4A, 4B, 4C, and 4D), and a same cap (i.e., 112 shown in each of FIGS. 4A, 4B, 4C, and 4D).
More specifically, FIG. 1 shows part of a bolster 102 of a rail car truck. The bolster 102 is attached at a first end to a side frame (not shown) that extends transverse to the bolster 102. The opposite or second end (not shown) of the bolster 102 is also attached to a second side frame (not shown). The bolster 102 of FIG. 1 includes a bolster bowl 106 configured to receive a center plate (not shown) of a car body (not shown) as described above.
FIG. 1 also shows an exploded view of one of these known constant contact side bearings 108 attached to a bearing pad 110 on the bolster 102. The bearing pad 110 provides a flat surface for securement of the constant contact side bearing 108.
An enlarged exploded view of this known side bearing 108 is better illustrated in FIG. 2 and an assembled view of this side bearing 108 is better illustrated in FIG. 3. The side bearing 108 includes a cap 112, an elastomer element 114, and a cage 116. This cage 116 (which is one of the four different cages of FIGS. 4A, 4B, 4C, and 4D) is configured to be secured to the bolster 102, and in particular is connected to the bolster 102 and/or the bearing pad 108 via mounting bolts extending through mounting holes 202.
The cage 116 illustrated in FIGS. 1, 2, and 3 includes a base 204 integrally formed with and connected to a side wall 206. The cage 116 also includes an integrally formed and connected key 208 that extends upwardly from the base 204 in the inner compartment defined by the cage 116. The side wall 206 of the cage 116 defines cap receiving channels 212A and 212B. The cap receiving channels 212A and 212B are defined in opposite sides of the side wall 206. These cap receiving channels 212A and 212B are configured to receive corresponding cap side wall extensions 216A and 216B of the cap 112 to facilitate the coupling of the cap 112 to the cage 116. The cap side wall extensions 216A and 216B are respectively received in the cap receiving channels 212A and 212B to enable the cap 112 to move vertically in relation to the cage 116 while at the same time preventing the cap 112 from rotating relative to the cage 116.
The top or top wall 218 of the cap 112 illustrated in FIGS. 1, 2, and 3 is configured to engage the bottom of the car body (or a plate thereon). The cap 112 moves vertically within the cage 116 based on the upward force exerted by the elastomer element and the downward force exerted by the car body. In certain instances, the vertical movement of the cage 116 in relation to the cap 112 is based on forces received via the bolster 102.
The elastomer element 114 shown in FIGS. 1 and 2 is configured to be positioned in the cage 116 between the base 204 of the cage 116 and inside the cap 112 to absorb the vibrations between the car body and the bolster, to counteract downward forces applied by the car body toward the bolster 102, and/or to apply an upward force against the bottom of the car body. The elastomer element 114 includes an interior channel 210 which has a diameter corresponding to a diameter of the key 208 of the cage 116. The key 208 is formed in a cross shape to engage the interior channel 210 of the elastomer element 114 at the four edges of the cross. The connected cage 116 and cap 112 enclose the elastomer element 114 as shown in FIG. 3. The range of vertical of travel of the cap 112 in relation to the cage 116 is based in part on the dimensions of the elastomer element 114 and other elastomer properties of the element 114. The Association of American Railroads (AAR) defines the acceptable or desired amount of travel of the cap in relation to the cage as the travel of the side bearing. The AAR specifies maximum travel distances based on the type of freight railroad cars utilizing the side bearing.
One known significant unsolved problem with these side bearings is that different cages have to be manufactured for use with the different elastomer elements. This problem is generally illustrated by FIGS. 4A, 4B, 4C, and 4D, which show commercially available different cages 116A, 116B, 116C, and 116D and different elastomer elements 114A, 114B, 114C, and 114D. The AAR specifies that different side bearings are to have certain compressive (e.g., preload) properties based on a type of freight railroad car. For instance, the side bearing may have to include an elastomer element with relatively rigid elastomer properties to support freight railroad cars that are heavier when empty. One known way to change properties of the elastomer element is to vary the diameter of the interior channel. Such elastomer elements with interior channels that have relatively larger diameters tend to be more compressible (e.g., support relatively lighter loads) compared to such elastomer elements with interior channels that have relatively smaller diameters. Different cages 116A, 116B, 116C, and 116D with different diameter keys must be employed to accommodate the different interior channels 210A, 210B, 210C, and 210D and diameters of the channels of these different elastomer elements. The exterior dimensions of the different cages (e.g., the cages 116A, 116B, 116C, and 116D) are typically the same to reduce manufacturing variations.
FIGS. 4A, 4B, 4C, and 4D generally show that the same cap 112 may be used with each of the combinations of different cages and different elastomer elements. The cap 112 includes an element cap post 402 that can fit within each of the interior channels 210A, 210B, 210C, and 210D of the elastomer elements. To accommodate all of the diameters of the interior channels, the element cap post 402 may not fully contact some of the interior channels that have relatively large diameters. In these instances, the elastomer element may have a relatively loose connection with the cap.
It should be appreciated from the above that manufacture of these known commercially employed side bearings includes selecting one of the cage and the corresponding elastomer element combinations. Each of the cages 116A, 116B, 116C, and 116D has a different respective key 208A, 208B, 208C, and 208D with a diameter that corresponds to a diameter of the respective interior channels 210A, 210B, 210C, and 210D of the elastomer elements. For example, the cage 116A includes the key 208A that has a relatively large diameter compared to the keys 208B, 208C, and 208D. The diameter of the key 208A is dimensioned to accommodate the interior channel 210A to enable the elastomer element 114A to attach to the cage 116A. In other words, the diameter of the key 208A is sized to have a relatively strong or tight fit or connection with the interior channel 210A when the elastomer element 114A is placed in the cage 116A during manufacture of the side bearing.
Similarly, the cage 116B includes the key 208B that has a diameter that corresponds to the interior channel 210B of the element 114B, the cage 116C includes the key 208C that has a diameter that corresponds to the interior channel 210C of the element 114C, and cage 116D includes the key 208D that has a diameter that corresponds to the interior channel 210D of the element 114D. In each of these different combinations, the same cap 112 can be connected to any of the cages 116A, 116B, 116C, and 116D as mentioned above.
Thus, it should be appreciated that to manufacture each of the different combinations illustrated in FIGS. 4A, 4B, 4C, and 4D, a manufacturer must make each of these different cages and the each of these different elastomer elements. In many instances, the cages are relatively costly and time consuming to manufacture in part because they are cast from steel or iron. Additionally, the manufacturer has to track, inventory, and package each of the different cages. Any mistakes in tracking the different cages can result in a cage being paired with a wrong elastomer element, thereby potentially violating AAR standards. Moreover, if the manufacturer does not properly inventory the cages, the manufacture of the ordered side bearing may be delayed until additional cages are made. It should be appreciated that the need to manufacture four different cages substantially increases manufacturing expenses, and waste time and energy. Accordingly, there is a need to solve these problems.